A decrease in fruit-eating animals, from primates to toucans, can make the problem of climate change worse, according to a study published in the journal Science Advances, entitled “Defaunation affects carbon storage in tropical forests”.

The Brazil Atlantic Forest, from which the researchers studied trees and animals of over 2,000, and 800 species respectively. Photo credits: Deyvid Setti and Eloy Olindo Setti; “Baía de Antonina vista da Serra do Mar2”; via Commons.

Nature works in wondrous ways, with the interdependence that unites the different species of living organisms an essential part of its backbone. A new study shows that we might be relying on frugivores more than we would have thought. Their absence will most likely bitterly demonstrate our need of them: their extinction might exacerbate climate change.

Researchers from the University of East Anglia argue that a decline in populations of fruit-eating animals like primates, tapirs, and large birds like the toucan can impact negatively on species of trees and ultimately on carbon capture. These relatively large-bodied animals play an essential role in the seed dispersal of large plant species; one of the authors, Professor Carlos Peres, explains that they account for nearly all of the dispersal of the large-seeded plants. The latter makes for greater wood density (than smaller plants), thereby being more efficient than smaller trees at tapping carbon dioxide. Conversely, if these populations of animals decrease in number, the propagation of the large seeds will be directly affected in the long run, resulting in a decreased tree canopy, and ultimately leading to less carbon dioxide flowing into plants from the atmosphere. On the other hand, the frugivores that are not hunted down by humans are only those that disperse small seeds (small birds, bats and marsupials).

The researchers explain that the diminishing tropical forests will cater for less carbon storage. Consequently, the built-up of the greenhouse gas in our environment will then distort the carbon cycle, leading to worsened climate change.

“When we lose large frugivores we are losing dispersal and recruitment functions of large seeded trees and therefore, the composition of tropical forests changes. The result is a forest dominated by smaller trees with milder woods which stock less carbon,” explains a PhD student involved in the study, Carolina Bello.

Therefore, logic dictates that if the lives of these animals are threatened by the activities of men — and they are indeed being threatened by hunters and illegal traders and habitat loss — we will most likely pay the bitter consequences in terms of climate change.

When we lose the animals, we are also losing the interactions that govern the healthy functioning of the ecosystem.

Hence, Professor Peres hopes that their study will encourage the authorities to focus on “faunally intact forests”, and not just on tackling deforestation.